Avoid the Rockies
I don't like flying over the mountains when another viable route is available. My route from PHX to Osh. First stop, Dalhart TX. KDHT. Bailey's flying service for fuel. Final fuel stop, Harlan, Iowa, KHNR. Quaint little airport with good fuel prices. This will give you 2 hours to OHS and plenty of fuel reserves.
From SoCal, I'd stop at St. Johns AZ for cheap fuel. Then on to KDHT and KHNR. Definitely doable with a long day starting at daylight.
The extra milage is worth not getting beat up over the mountains. Overall it isn't that much farther for the Southern route.